Interposer plates with inserted metal contact members in apertures extending through the plates are used for forming electrical connections between contact pads on opposed substrates.
The pads on the substrates and the contact members are typically arranged in closely spaced rows and columns. Each plate may support 3,000 or more contact members. The contact members are inserted in the apertures and must be held in known positions in the apertures in order to assure proper engagement with pads on the substrates and to permit attachment of solder balls. The contact members must be supported in the plates in known locations during attachment of solder balls, during reflow soldering of attached solder balls to form electrical connections with pads on an underlying substrate and during stressing of spring contacts on the contact members to form electrical connections with pads on substrates.
The close spacing of the contact members means there is limited space in the plate for forming physical connections between the plate and contact members inserted in through apertures.
The connections between the contact members and the plate should permit withdrawal of a contact member when the contact member is deformed or needs to be replaced and should permit reinsertion of another contact member in the same aperture.
Also, connections between the contact members and the plate must not bow or vary the shape of the plate. Bowing of the plate alters the vertical positions of contact members in the plate and makes it unsuitable for attachment of solder balls to solder tabs and unsuitable for soldering on a substrate. Additionally, bowing the plate results in unacceptable uneven stressing of cantilever contacts on contact members in the plate and impairs electrical connections between cantilever contacts and substrate pads.